The hydrogenation of 2, 3-dimethylpyrazino [2, 3-b] quinoxaline 1 and 2-phenylpyrazino [2, 3-b] quinoxaline 2 leads to the corresponding 5, 10-dihydroderivatives 3 b and 4 b. LiAlH4 reduction of 2, of 2, 3-dimethyl-6, 7-diphenylpyrazino [2, 3-b] pyrazine 8 and 2, 6, 7- triphenylpyrazino [2, 3-b] pyrazine 9 furnishes the corresponding 1, 2, 3, 4- tetrahydroderivatives 7, 10, and 11. NaBH4 reduction of 2 leads to a mixture of 4 b and 7. ...